The 20-year-old reportedly shot and killed his mother, Nancy Lanza, who was a kindergarten teacher at the school, at her residence in Newtown. He then reportedly drove to the elementary school and fired dozens of rounds in two rooms before shooting himselfin the kindergarten classroom.

Adam's father, Peter Lanza, refused to comment on the shooting, according to the Stamford Advocate. Following the shooting, police went to Lanza's house for a welfare check and remained at the home for about thirty minutes.

Lanza and Adam's mother Nancy divorced in 2008.

CNN reported the principal and a school psychologist were killed in the shooting, which was reported at 9:41 a.m. The News York Times' Libor Jany also cited witnesses who are saying the school's principal was killed.

News reports detailed heroic acts by teachers, including one who physically stood in front of the door to keep it shut and protect her students.

First-grade teacher Kaitlin Roig told ABC News she locked her students and herself in the bathroom and was so intent on keeping them alive she initially refused to unlock the door for the police, fearing the gunman was trying to trick her into opening the door.

Following the shooting, Police were "questioning a handcuffed suspect in connection with the Newtown school shooting," the Connecticut Post tweeted. A witness told Jany that a man "was led out of the woods by police in handcuffs." Connecticut State Police Lt. J. Paul Vance told reporters that there was only one shooter.

The confusion may have been caused by the fact that the shooter was carrying his older brother's ID, Reuters' Matthew Keys tweeted around 4 p.m. on Friday. The Associated Press reports that a law enforcement official mistakenly transposed the brothers' first names.